This invention relates generally to a double-walled helical seamed structural vessel and a method of forming same, the vessel having a helically wound stiffening spacer between its walls.
A structural vessel of this general type is set forth in the aforementioned related application as a unique and improved construction over prior art double-walled and reinforced single walled tubular vessels. In accordance with my earlier approach as therein set forth, an inner tubular liner and an outer tubular shell spaced about the liner each comprise helically curved strips of material, with helically wound spaced means between the liner and shell spanning contiguous edges at successive turns of the liner as well as spanning contiguous edges at successive turns of the shell. The contiguous liner edges are seamed together as by welding, and the spacer means secured to the strips forming the liner and shell via such welding means by disposing the spacer at the contiguous edges of the liner and at the contiguous edges of the shell, and by securing the spacer to the liner and shell by way of the welds used in seaming together these contiguous edges. The structural integrity and strength of the vessel are therefore vastly improved. Also, the process carried out for fabricating such structural vessel is simplified, labor saving and economical.
Although this design achieves and even surpasses all its expectations, it has been found that by using a slightly different fabricating technique, a double-walled, helically seamed structural vessel can be formed even more quickly and efficiently than before, while enhancing the structural integrity of the vessel. The need for tracking the narrow webs of the spacer on one another in accordance with my earlier approach, can be avoided. And, because the web tips of the inner beam section slightly fan out when helically wound, and the tips of the outer beam section slightly contract when helically wound, care must be taken when cutting the beam along an undulating line so as to ensure matching web tips between the beam sections during the fabricating process.